This invention relates generally to nuclear reactors and more particularly, to apparatus for enhancing the performance of the steam dryers in a nuclear reactor pressure vessel.
A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide typically is spaced above a core plate within the RPV. A core shroud, or shroud, typically surrounds the core and is supported by a shroud support structure. Particularly, the shroud has a generally cylindrical shape and surrounds both the core plate and the top guide. There is a space or annulus located between the cylindrical reactor pressure vessel and the cylindrically shaped shroud.
Heat is generated within the core and water circulated up through the core is at least partially converted to steam. Steam separators separate the steam and the water. Residual water is removed from the steam by steam dryers located above the core. The de-watered steam exits the RPV through a steam outlet near the vessel top head.
The flow of steam through the dryers can be unbalanced or mismatched, with much of the steam flow preferentially passing through the top of the dryer vanes. At increased power levels of the reactor, increased steam flow may cause the steam velocity to exceed the breakthrough velocity in local regions of the dryer vanes. The dryer ceases to remove moisture droplets from the steam in those areas where the breakthrough velocity has been exceeded. Wet steam that breaks through, or exits the dryer, then can cause undesirable effects in the rest of the power plant. In addition to the potential for erosion of the metal components, the excess moisture can transport activated particulates from the reactor to the pipes, turbines and heat exchangers which are downstream of the separator which can increase the dose rate in the turbine hall, and make equipment maintenance more difficult.
In one aspect, a flow control apparatus for a boiling water nuclear reactor steam dryer is provided. The steam dryer includes at least one discharge plenum. The flow control apparatus includes a support member, an elongate perforated plate member coupled to the support member, and at least one positioning member coupled to the support member.
In another aspect, a steam dryer for a nuclear reactor is provided. The steam dryer includes a plurality of dryer vanes, at least one discharge plenum, and a flow control apparatus. The flow control apparatus includes a support member, an elongate perforated plate member coupled to the support member, and at least one positioning member coupled to the support member.
In another aspect, a steam dryer for a nuclear reactor is provided. The steam dryer includes a plurality of dryer vanes, at least one discharge plenum, and a flow control apparatus. The flow control apparatus includes a support member, an elongate perforated plate member coupled to the support member, at least one positioning member coupled to the support member, at least one lip extending longitudinally along a first side of the perforated plate member and substantially perpendicular to the perforated plate member, a first adjustable sealing member coupled to a first end portion of the perforated plate member, and a second adjustable sealing member coupled to a second end portion of the perforated plate member.